Temperature control device



April 26, 1938. R. L. UHL 2,115,598

TEMPERATURE CONTROL DEVICE I FiIed Aug. 6, 1935 2 Sheets-Sheet l inventor: Robert L. Uhl

by 49W /9 Hls Attorney.

R. L. UHL

TEMPERATURE CONTROL DEVICE April 26, 1938.

Filed Aug. 6, 1935 Fig 7. Li

2 Sheets-Sheet 2 by if K 9 Inventor: ULf Robert L. Uhl,

Hi5 Attorneg.

Patented Apr. 26, 1938 UNITED STATES PATENT OFFICE Robert L. Uhl, Ontario, CaliL, assignor to General Electric Company, a corporation of New York Application August 6, 1935, Serial No. 34,909

9 Claims.

This invention relates to temperature control devices, more particularly to devices for controlling an electric circuit in accordance with temperature changes, and it has for its object the provision of an improved device of this character which is simple and inexpensive to make and which is reliable and eflicient in its operation.

This invention contemplates the provision of an improved temperature control device wherein the temperature responsive element is arranged both to act as the motive means for operating the switch, or other control member, and also as the means for causing the control member to be moved with a snap action.

In accordance with this invention, in one form thereof a bimetallic thermostat is provided. One end of the thermostat is fixed, while its other end is free to move in response to temperature changes. Between these fixed and free ends,

there is provided a resilient portion of reverse curvature, preferably formed by two reversely arranged loops.

Adjacent the free end there is a bearing, and resting on this bearing and also on the free end is a spacer which is proportioned to tension or stress the resilient portion of reverse curvature. This portion is so arranged and tensioned that it moves the thermostat between its controlling positions with a snap action.

For a more complete understanding of this invention, reference should be had to the accompanying drawings in which Fig. 1 is a vertical central sectional view of an electric flatiron provided with a temperature control device embodying this invention; Fig. 2 is a plan view of the fiatiron of Fig. l with the cover removed so as to illustrate certain details of construction; Fig. 3 is a bottom plan view of the temperature control device used in the electric iron of Figs. 1 and 2;

Fig. 4 is a plan view of a temperature control device of modified form arranged in accordance with this invention; Fig. 5 is an elevation of the control device of Fig. 4; Fig. 6 is a bottom plan view of the temperature control device of Figs. 4

and 5; Fig. 7 is a vertical sectional view of an electric flatiron provided with a temperature control device of still another modified form of this invention; Fig. 8 is a plan view of the iron shown in Fig. '7 with the cover removed so as to illustrate certain structural details; Fig. 9 is a bottom plan view of the temperature control device used in the iron of Figs. '7 and 8; Fig. 10 illustrates a control or adjusting member used in the irons of Figs. 1 and 2, and also in Figs. 7 and 8, together 55 with a temperature scale provided to assist in 'mounted. The recess adjusting the temperature setting of the control device; and Fig. 11 illustrates a bimetallic thermostat arranged in accordance with this invention, but showing the thermostat before it is assembled with the thermostat organization. 5.

Referring to the drawings, this invention has been shown as applied to electric flatirons. ItiS to be understood, however, that the thermostat has general application. Thus, it may be used to control wafile irons, grease kettles, percolators, 10 etc.

Referring more particularly to Figs. 1, 2 and 3, the electric fiatiron comprises a body member or sole plate In made of a suitable heat conducting material, such as aluminum alloy or cast iron, 15 within which is cast a suitable electric heating unit I I. The upper portion of the body member ID is enclosed by a cover member I2, which is secured to the body member in any suitable manner, as by means of screw fastening means (not 20 shown). The body member is provided with a handle structure I3, which in Fig. 1 has been shown in but fragmentary fashion. The heating unit Il may be of any suitable type, but preferably will be of the sheathed type, such as de- 25 scribed and claimed in the United States patent to C. C. Abbott No. 1,367,341, dated February 1, 1921.

In the upper portion of the sole plate I0 is an elongated recess II, in which is secured a tem- 30 perature responsive control device for the heating unit II. As shown, this recess I4 at its forward end is provided with a still deeper recess, or well I5 in which the temperature control device is I5, as shown, extends 35 downwardly in the sole plate to a level below the lower edge of the heating element II. In width the recess I5 is somewhat narrower than is the width of the recess I4, as clearly shown in Fig. 2. 40

The temperature control device comprises a supporting plate I6, which is supported in the recess portion I4 over the recess I 5. The supporting plate I6 is secured to the walls of the sole plate surrounding the recess I5, by means 45 of screw fastening means ,I'I,

The temperature control device further comprises a suitable thermostat, shown as a bimetallic element I8 made of two strips of metal of dissimilar temperature coeflicients of expansion,

such as invar and Monel metal, the two strips being securely brazed or welded together lengthwise.

I'he bimetallic thermostat member I8 has a portion I! of reverse curved form, that is, it has a sinuow form, preferably having two loops ltd and 11% arranged in reverse order, as clearly shown in Fig. 3. This arrangement gives the bar ill a distorted S=shape. The ends of the portion it) of reverse curvature terminate in straight portions it and 2!! which extend outwardly from the adjacent arms oi the associated loops substantially at right angles thereto, and which. are arranged in substantial alignment each other, when the member it is assembled in the thennostat organization, as shown in Fig. 3. The loops l tie and till) preferably will have the same length measured from the alignment of the end portions iii and El.

The end 2i of the thermostat it is rigidly secured to a support 22, which in turn is rigidly secured to the supporting plate it. As shown, the support 22 is rigidly secured to the plate it by means of a rivet 23, and is provided with a portion 2 extending downwardly from the plate 56 at right angles to the main portion of the support 22'. The end portion 29 of the thermostat is rigidly secured to the portion 24 by means of a screw The support 22 is provided with an upright car 26 whichextends upwardly through an aperture provided for it in the supporting plate l6, as shown in Figs. 1 and 2, and which is arranged to be connected with a suitable lead 2?, as by means of screw fastening means 23. The supporting plate 22 is electrically insulated from the plate l6 by means of a suitable sheet 29 formed of some suitable electrically insulating material, such as mica.

The end 20 of the thermostat I8 is free to move in response to changes in temperature, and

the movement of this end is utilized to operate a suitable electric switch. This switch comprises a contact 30 carried by the free end 20 and a contact 3i which cooperates with the contact 30. The contact 3| is carried by a contact plate 32 which is rigidly secured to the plate l6 as by means of a rivet 32a. The contact plate '32 is provided with an upright ear 33 that is projected through an aperture provided for it in plate 16, and is arranged to be connected with a lead 34 as by means of a screw 35. The contact plate 32 is insulated from the supporting plate l6 by means of the mica insulating strip 29. A sheet of mica 35a, similar to the mica. sheet 29, is placed on top of the plate l6 to insulate the rivets 23 and 32a from the plate I6. The mica sheets 29 and 35a also insulate the upright ears 26 and 33 from the supporting plate.

Positioned adncnt and substantially opposite the free and!!! of the thermostat is a bear-'- ing 36. Interposed between the bearing 36 and the free end 20 is a. rigid spacer member 31 formed of a suitable electrically insulating material, such as porcelain. The spacer member 31, as shown more clearly in Figs. 1 and 3, is provided in its ends with bearing seats, one or which rests on the bearing 36, while the other rests on the free end of the thermostat. The bearing 36 is so positioned, and the spacer member 31 is so proportioned that when it is inserted between the bearing 36 and the free end of the thermostat, it places the portion IQ of reverse curvature under compression, that is, tensions it so that the free end normally applies a predetermined Iorce or end thrust to the spacer member 31, and also forcesthe' contacts 30 and 3i together. This latter force is increased by virtue of the initial form that is given the bimetallic thermostat l8. Thus, when the bimetallic thermostat is not assembled, it has a somewhat arran e difierent form than when assembled with the organization of parts that make up thetemperature control device shown in Fig. The form that the thermostat has initially, or when it is unrestrained, is shown in Fig. 11. as there shown, the straight portion at at the movable end of the bar is not in substantial alignment with the straight fixed portion Zil, but is sup ported in a position above and at an appreciable angle to a straight line containing the portion 2i; and moreover, the loops that and life are open, that is, are not compressed as they are in the assembly. When the member it is assembled the loops are compressed and the portion 2 1i brought into substantial alignment with straight portion 2i. This causes the contacts Jill and ill to be urged together with a considerable force in addition to the force urging the contacts together due to the arrangement of the spacer The bearing 36 is carried by an arm 38, which, as shown (Fig. 1) is provided with a substantially upright portion 39 that carries the bearing 36, and a portion 49 arranged at right angles to the portion 39 and which extends over the sup-- porting plate IS. The portion 40 is pivotally secured to the supporting plate by means of a rivet 4!. is an arcuate shaped gear rack 42. Meshing with this gear rack is a gear43 that is mounted upon a shaft 44. The shaft 44 is mounted in a support 45 which in turn is rigidly secured to the supporting plate l6 by means of ears or tabs 46 provided on the support 45 and passed through apertures provided for them in the supporting plate IS, the tabs being turned or clinched on the supporting plate 16, as shown in Fig. 3. The shaft 44 protrudes through an aperture provided for it in the casing l2 to the exterior of the iron, where an adjusting knob 48 is secured to the protruding portion of the shaft.

The support 45 carries a stop member 49 with which a stop washer 50 mounted on the shaft 44 cooperates. The stop washer 50 is provided with a stop portion whose opposite ends cooperate Carried on the end of the portion 40 with the stop 49 to limit the adjusting motion pression spring 5Ia surrounds the shaft 44 and holds the stop washer in place against the under surface of the support 45. The lower end of the spring rests on an abutment secured to the shaft 44.

The thermostat l8 moves between a pair of controlling positions, one of which is defined by the fixed switch contact 3|, and the other of which is defined by means of a stop 52 mounted on the supporting plate 22 for the thermostat.

It will be understood that the leads 2! and 34 connected respectively with the upright cars 26 and 33 will be connected in the heating circuit of the iron so that when the thermostat-is in the closed position, as shown in Fig. 3, the-heating circuit for the unit I I will be closed, whereby the unit will be energized to apply heat to the sole plate l0, and that when the thermostat is open, or moves to its controlling position against the stop 52, the heating circuit will be opened whereby the unit l I will not apply heat to the sole plate. As shown, the iron is provided with the usual twin pin electrical supply terminals 53 and 54, which are arranged to receive the usual supply plug of twin supply conductors. The terminal 53 is electrically connected to one of the terminals 55 of the heating unit ll, while the other pin 55 is electrically connected to the lead 27!.

The other lead 34 is electrically connected with the other terminal 56 of the heating unit. It will be observed that in view of these connections, when the thermostat is open, the heating unit will be de-energized, whereas when it is closed this unit will be energized.

In the operation of the thermostat, it will be understood that when the temperature of the thermal element I8 is below a predetermined temperature, it will be in its controlling position to close the switch. If when the thermostat is in this position, the iron be plugged-in to an electrical supply source, the heating unit II will be energized through the thermostat to supply heat to the sole plate l0. By continued application of heat to the sole plate the temperature of the plate will increase, and as the temperature of the plate increases, the thermal element I8 will tend more and more to move from its position shown in Fig. 3 to its open position wherein the free end 20 rests against the stop 52. This tendency of the thermostat to move, however, is opposed by the resilient force holding the movable contact 30 against the stationary contact 3| applied by the spring portion l9' defined by the reversely arranged loops I9a and I91). Eventually, however, the plate III will attain a predetermined maximum temperature at which the tendency of the thermostat to move downwardly,

as viewed in Fig. 3, will overcome the resisting force applied to it by the curvature I9, whereupon the thermostat will begin to move from its closed position. The spring portion 19 will oppose this movement with a decreasing force until the free end 20 of the blade l8 moves to and through a critical position, whereupon it will assist movement of the thermostat to the open switch position beyond the critical position with a force which rapidly increases. The critical position of the thermostat lies substantially in an imaginary straight line directed between the end of the thermostat carrying the contact 30 and the point of support of the fixed end 2| of the thermostat. This line joins the movable end of the thermostat with that portion of the thermostat where the straight end portion 2| joins the adjacent loop I917.

The spring portion l9 will tend to hold the thermostat in its open position, and the thermostat will remain in this open position until the temperature of the sole plate l0 cools to a predetermined minimum at which the thermostat will overcome the resilient force applied to it by the spring l9 and will move toward its critical position, the spring I9 resisting its movement to this position with a decreasing force. When the thermostat moves through the critical position, the spring l9 assists it in closing the switch. In this manner, the thermostat maintains a predetermined temperature which is a mean between the maximum temperature at which the switch is opened and the minimum temperature at which.

the switch is closed.

It is to be noted that the change in overall length between the fixed and movable ends of the thermostat, as it moves to open and close the switch, is extremely small, and because of this, the end thrust pressure of the thermostat on the spacer 31 remains substantially constant. This end thrust pressure, however, can be varied somewhat during the heating and cooling cycle, by making the loops I91: and l9b of unequal length.

The temperature adjustment of the thermostat is effected by shifting the relative position of the support 24 of the fixed end of the thermostat and the bearing 36 for the spacer 31. accomplished by adjusting the knob 48. To increase the temperature setting, the knob is adjusted to move the bearing 36 in a counter clockwise direction, as viewed in Fig. 3. A reverse adjustment reduces the temperature setting. In order to assist the operator in adjusting the setting of the iron, a suitable temperature indicating plate 58 (Figs. 1 and 10) is attached to the upper surface of the cover l2. The plate 58, as shown, is provided with temperature indications High and Low, together with temperature gradua-- tions between these indications.

In the form of the invention shown in Figs. 4, 5 and 6, the support for the fixed end of the thermostat is shiitable .to adjust the temperature setting of the control device, rather than the bearing adjacent the free end of the thermostat. As shown in this form, a supporting plate 60 is provided which is arranged to be attached to the device to be heated. Mounted beneath this plate 60 is a thermostat 6| similar to the thermostat l8 of the first form described. One end 62 of this thermostat is rigidly secured to a supporting member 63, which is provided with a depending portion 64 to which the end 62 is rigidly secured.

This is The opposite or free end 65 of the thermostat bears on a spacer member 66 which in turn rests upon a fixed bearing member 61. The bearing member 61 is rigidly secured to a depending portion 68 of the supporting plate 60, as clearly shown in Fig. 5. The member 6! is insulated from the member 64 in any suitable manner, as by means of mica washers (not shown).

Mounted in the plate 60 is a disc 10 which carries a crank pin ll eccentrically to the axis of the disc. The crank pin ll is received in a forked end 12 of the arm support 63 so that when the disc 10 is rotated, the arm 63 is rotated, which operation shifts the position of the fixed end 62 of the thermostat relative to the bearing 61. The disc 10 is supported on, and is operated by an adjusting stud or shaft 13 which is mounted in a bracket '14 attached to the upper surface of the plate 60. This shaft is provided with a suitable stop member 15 that engages the stop 16, these members being arranged as are the corresponding elements of Figs. 1 and 2.

The movable end 65 of the thermostat carries a contact 11 which cooperates with a fixed contact 18 carried by a contact arm 19. This contact switch arrangement is similar to that shown in the first form. 'A stop is provided to limit the open position of the switch. This 'stop is mounted on a stop plate 8| which is similar in construction to the switch contact arm 19. Suitable sheets of insulating material, such as mica sheets 82 and 83, are positioned on opposite sides of supporting plate 60. These sheets as well as the contact arm 19 and the stop plate 8| are riveted to plate 60.

With the exception of the temperature adjustment this form operates as does the first form.

In the form shown in Figs. 7, 8 and 9, the temperature control device is somewhat larger than in its previous forms, but is similar in construction to that shown in the first form described in Figs. 1, 2 and 3. The sole plate 84 of the iron in this case is provided with a larger recess 85 to accommodate the thermostat. The thermostat, in this case, comprises a supporting plate 86 beneath which is mounted a thermostat 81 88 of this thermostat is rigidly secured to a suplid till

port 85 which also functions as a terminal for the thermostat. This support lid is carried by plate till; The free end lid of. the thermostat bears on a spacer member ill which in turn rests on a bearing 92. The free end of the thermo stat carries a switch contact $53 which contacts with a stationary contact or. The latter contact is carried by a contact strip 95 which'is mounted on the plate lit.

The bearing 92 is mounted on a sector-shaped plate 95, which in turn is secured to a second sector-shaped plate til. These plates are pivotally mounted to rotate on a pin so which in turn is supported on the plate lit. The plate ilii may be adjusted relative to the plate ill, and for this purpose is secured to theplate 9?! by means of a screw and slot connection d9. Normally, however, these plates are moved as a rigid unit. The plate ill on its outer edge is pro vided with a rack lilo with which a gear till mounted upon an adjusting shalt tilt meshes. The adjusting shaft W2 is provided with an adjusting knob Mil on the exterior of the iron. The contact strips 89 and 85 are electrically insulated from the plate to by means of a sheet of mica ldd'. A similar sheet [1% is positioned above the plate to insulate the supporting rivets lilii provided for the contact strips and the mica sheets. This thermostat operates in substantially the same fashion as the form described in Figs. 1, 2 and 3, in that temperature adjustment is eii'ected in the same manner by adjusting the knob Hi3 which shifts the fixed bearing @2 relative to the fixed end oil of the thermostat.

It will be observed that the plate lid, as in the previous forms, supports the complete mechanism of the thermostat in thermal relation with the iron.

While I have shown particular embodiments of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A temperature control device comprising a bimetallic temperature responsive element having one end free to move in response to temperature changes, the major portion of the length of said element being provided with a pair of reversely arranged loops of substantially the same length so that when said element is subjected to temperature changes one of said loops contracts and the other expands in substantially equal amounts to maintain a substantially constant overall length between the ends of said element and so that said free end moves substantially in the arc of a circle, a pivoted rigid member bearing on said free end and moving with it in its plane of movement as said free end moves, and a control element operated by the movement of said free end.

2. A temperature control device comprising an elongated bimetallic temperature responsive ele-- ment having two relatively short straight end portions in substantial alignment, one of said end portions being free to move responsively to temperature changes, and the major portion oi the length of the element between its ends being formed into reversely arranged loops having predetermined lengths relatively to each other on opposite sides of a line directed substantially through said straight ends, a bearing opposite aliases said free end, and a rigid member having one end resting on said bearing and its other end on said free end of said element to compress said loops, said loops thereby functioning to cause said element to snap between controlling positions, and as the temperature changes, one of said loops contracting while the other expands by amounts depending upon their lengths so that the end pressure of said element on said hearing is controlled within predetermined limits as said element moves between said controlling positions.

3. ll. temperature control device comprising an elongated bimetallic thermostat bar having a pair of reversely arranged loops and end portions projecting from said loops in substantial alignment with each other, a support for one of said end portions, a bearing seat adjacent the other of said end portions, a rigid spacer bar resting on said other end portion and also on said bearing seat arranged to tension said portion of reverse curvature, whereby said portion moves said bar with a snap action between controlling positions, the lengths of said loops being substantially equal measured from the alignment of said end portions so that when said temperature varies one contracts by an amount substantially equal to the expansion of the other, thereby to maintain the pressure on said spacer bar substantially constant as said thermostat bar moves betv. en said controlling positions and means for changing the relative positions oi said support and said bearing seat so as to vary the temperature setting of said control device.

i. A temperature control device comprising a resilient bimetallic thermostat having a portion of reverse curvature formed of reversely arranged loops of substantially the same length and having end portions projecting therefrom in substantial alignment with said other, means supporting one of said end portions, a bearing seat adjacent the other of said end portions, a rigid spacer bar resting on said other end portion and also on said bearing seat arranged to tension said portion of reverse curvature, and means for changing the position of said hearing seat so as to change the temperature setting of said device.

5. A temperature control device comprising a support, bimetallic thermostat having a pair of reversely formed loops with their two ends projecting in substantial alignment from the loops and said loops having substantially equal lengths measured from the line of said ends, means rigidly securing one of said ends to said support,

a bearing opposite the other of said ends, a spacer bar having one end resting on said bearing and its other end resting on said other end of said thermostat, an arm carrying said bearing pivotally mounted on said support, a gear segment carrled by said arm, a shaft, a gear on said shaft meshing with said gear segment, and means for adjusting said shaft to vary the position of said bearing.

6. A. temperature controldevice comprising a support, a bimetallic thermostat having a pair of reversely formed loops with their two ends projecting in substantial alignment from the loops, an arm pivotally mounted on said support, means rigidly securing one end of said thermostat to said arm, a bearing opposite the other end of said thermostat, a spacer bar having one end resting on said bearing and its other end resting on said other end of said thermostat, an eccentric mounted on said support cooperating with u said arm so that when rotated the angular position of said arm is varied, and means for adjusting the position of said eccentric. I

7. A temperature control device comprising a support, a fixed switch contact carried by said support, a bimetallic thermostat having reversely arranged loops defining a portion of reverse curvature, and also having a pair of substantially straight portions, at the ends projecting from said loops respectively, said straight portions being substantially out of alignment and said loops being open when said thermostat is free, a contact carried by one of said straight portions, a movable bearing member for said one straight portion mounted on said support and means for rigidly securing said other straight portion to said support so that when said one straight portion is mounted in its bearing, said straight portions are in substantial alignment, said loops are compressed and of substantially equal lengths, and said contacts are closed at room temperature.

8. A temperature control device comprising an elongated bimetallic temperature responsive element having two straight ends in substantial alignment, one of the ends being free to move responsively to temperature changes, and the major portion of the length of said element between its two ends being formed into a single pair of reversely arranged loops having predetermined lengths relative to each other measured from a line passing substantially through said straight ends, a bearing opposite said free end, and a rigid member having one end resting on said bearing and its other end on said free end to tension said loops, said loops thereby functioning to cause said element to snap between controlling positions, and as the temperature changes one of said loops contracting while the other expands by amounts depending upon their respective lengths so that the end pressure of said element on said bearing is controlled within predetermined limits as said element moves between said controlling positions.

9. A temperature control device comprising a support, a fixed switch contact carried by said support, a bimetallic thermostat having reversely arranged loops defining a portion of reverse curvature, and also having a pair of substantially straight portions at the ends projecting from said loops respectively, said straight portions be- ,4

ing substantially out of alignment and said loops being open when said thermostat is free, a bear ing member for one of said straight portions mounted on said support and means for securing the other of said straight portions to said support so that when said one straight portion is mounted in its bearing, said straight portions are in substantial alignment and said loops are compressed.

ROBERT L. UHI. 

